Transcript David Weaver: This is a fabulous effort! There are a few things missing and a few other minor comments.

David Weaver:
This is a fabulous effort! There are a few things missing and a few other minor
comments. The whole biological (food, waste, air, etc.) issue is missing.
Andrew Duncan
Katherine Colla
Joe Kempton
April 26, 2006
Another
Presentation
Project Description
The object of Project 3 is basically to design a means by which the Physics
Phreaks can travel to a planet in orbit around Alpha Centauri A. The group
must vacation there for a year, and then come back to Earth with
souvenirs.
We need to take into consideration our means for living on a ship in
order to live comfortably (or at all) for the amount of time we are going to
be traveling. This would include propulsion (based on ship chosen), fuel,
food, water, air, and relativistic effects.
Upon deciding what type of ship the Physics Phreaks are going to use on
their voyage into outer space, they must apply the relativistic effects in
order to figure out how long they will be traveling. The ship will be traveling
at a constant acceleration until they reach the midpoint of the journey,
where they will begin deceleration until they reach their destination. We
must take into consideration the effects, along with the known distance
from earth to the star to determine the length of the trip.
Timeline
The following Timeline is a representation of the hard work and dedication
exemplified by the group, the “Physics Phreaks”.
Wed., March 29th – We were introduced and reviewed P3
Mon., April 3rd – Group Meeting #1: Discussed concepts of Project and
brainstormed some ideas
Wed., April 5th – Group Meeting #2: Decided on type of ship
Mon., April 10th – Discussion of Project in class. Work on gathering
information.
Fri., April 14th – Meeting # 3: Struggled with math, only to find out we
were wasting or time.
Sat., April 15th – Research continues. Andy discovers Space
calculator used for relativistic calculations ….Jackpot!
Mon., April 17th – Picked David’s brain concerning Time Dilation
Fri., April 21 – Meeting to begin TIM and create graphics
Sat., April 22nd – Complete TIM for presentation.
Mon., April 24 – Cover some holes in the TIM / Prep presentation.
Destination
Alpha Centauri is located approx.
4.4 light years away. It has a mass
of 2.17 x1030 kg, a diameter of
approx. 7.73 x 108 m, and a
surface temperature of 5442 oC
Alpha Centauri also known as:
Rigil Kentaurus
located in the foot of
Centaurus Constellation
Final Destination
Being that Alpha Centauri is much too hot to land on and explore, we are going to
attempt to land on one of the three planets believed to be orbiting the star. The
planets are named Curley, Moe, and Larry. We are planning to land on Curley, as
it is the closest planet to Alpha Centauri, which will make it easier to observe. An
exploratory pod, Mini C3 will be our means of travel from space to Curly.
Voyage Vehicle
The Physics Phreaks have determined that the best interstellar
travel can be accomplished using a solar sail, sometimes
referred to as a light sail.
How does a Solar Sail
work?
Solar sails are composed of large flat smooth sheets
of very thin film, usually covered with a reflective
coating, and supported by lightweight structures
attached to a central spacecraft (where we reside).
The sails use aluminum Mylar (a strong, thin polyester film), which is
very large and thin, not to mention hard to work with.
David Weaver:
The result is a huge mirror. The force generated by the sun shining on this
surface, which is created by transferring the momentum from the light
I thought you were going to accelerate at 1 g which isn’t quite snail-like, is it?
particles (photons), propels the object forward. This may show a tiny
force, but this snail-like acceleration results in the achievement of
velocities large enough to cover immense distances without using fuel.
During our voyage, we can change the angle of the sails to better propel
the spacecraft toward the desired direction similar to wind pushing the
sails of a sailboat.
CENTAURUS 3
We have named our Voyage Vehicle
CENTAURUS 3 or C3.
It was constructed in space over a
span of many years. It consists
of various materials, including
conventional light sail film
(mylar) with a thin film aluminum
layer deposited on one side.
The main body of the ship (center),
consists of living quarters, a
place to harvest food, and an
exploratory vehicle, called
MINI C3.
C3 Stats
•
•
•
Sail Configuration: Circular Spinner
Sail Information
• 3600 m diameter
• Area: 10,000,000 m2
• Total mass: 1000 kg
Top speed: 0.95 c
Lorentz Contraction
Lorentz contraction is the shortening of an object along a direction of
motion as speed approaches the speed of light. This contraction can be
measured by both the observer, who is at rest with respect to the
moving body, as well as the observer from inside the moving body with
respect to objects outside the moving body. For instance if we had a
meter stick on the side of the road and a car traveling along the road at
a relativistic speed of .95 the speed of light, the measured length of the
meter stick from inside the car would be .312m or 31.2cm. Likewise an
observer on the sidewalk would measure the car at 31% of its at-rest
length.
Contraction of space
The Lorentz contraction can help us understand how distances
contract at relativistic speeds. As C3 travels through space
approaching a velocity near the speed of light (0.95c), our
measured distance in space from us to Alpha Centauri contracts to
give us a fraction of the original measured distance from earth. This
changes our actual traveling distance from 4.16X1016m to
1.30X1016m, almost 1/3 of the original distance.
This contraction would be correct if we maintained a constant velocity of 0.95c
throughout the entire mission. For our mission we only reached 0.95c at the
midpoint, therefore the distance will be incorrect for our mission.
Time Dilation
Time dilation is the phenomenon where the observed rate of time from an
observer's point of view is different from the rate of time recorded by an
object with respect to its velocity. The following graph illustrates how
insignificant the effect of time dilation is for velocities as great as half
the speed of light, but how dramatic it becomes as we draw closer and
closer to the speed of light. By the time we reach .90 the speed of light,
for each day on board, two and a quarter days pass for an observer
located on earth. If we continue to accelerate to 0.99999999999999 c,
for every day on board, nearly twenty thousand years pass for the
observer on earth.
David Weaver:
You should consider how long your entire trip took for you and for earth-bound family
and friends (and teachers).
Distance to Star
Due to relativistic effects, you can see the distance change for
observers on Earth versus travelers in C3. The graph also shows the
difference in time.
David Weaver:
This would be a really good place (or nearby) to invoke one of the postulates of the
Special Theory of Relativity: the constancy of the speed of light. If you divide the total
distance by the time, you get the same average velocity in each case.
Velocity vs. Time
It is important to mention that our data is a bit flawed based on the
realization that our max velocity(0.95 c) is only reached at the midpoint
of the mission.
David Weaver:
I did provide y’all with the Excel file to figure out the actual (?!) information. Please
consider doing a couple of new slides with the corrected (?!) information as errata
sheets that you can place at the end and refer to in the main presentation (like here).
Acceleration vs. Deceleration
For the first half of the voyage we will be accelerating
at one G or 9.8m/s2.
For the second half of the voyage we will be
decelerating at a 9.8m/s2.
Aberration of Light
The effect of aberration describes how accelerating at relativistic speeds
that the photons from these stars come in from all directions into the
frontal view. We can see how the whole field of view seems to shrink in
the direction of travel. Even photons from stars that we know are
behind us come into view while traveling in a forward direction.
The pictures above show an example of the aberration of light aif you were
going to travel to Orion.
Doppler Shift
Image source www.astro.ucla.edu
While we observe matter in space which enmities light that is moving away
from us, we see light that has a longer wavelength than it had when it
was emitted, causing that light to appear red. Also we can observe an
approaching space matter and see light that is shifted to a shorter
wavelength that would appear to be blue.
Image source www.lcse.umn.edu
We captured this picture of
Alpha Centauri as we were
preparing to land on Curly.
David Weaver:
As I will talk more about later, I’m giving a lecture at a national physics teachers meeting
about project-based
I mentioned
that
I’ll be
asking
y’allustoofrespond
to a survey
We wanted to physics.
have something
to take
with
us to
remind
our journey
about project-based
vs.that
traditional.
I will
alsowould
be asking
that are interested to
and decided
a souvenir
photo
be a those
good idea.
answer a few questions on video to include in my presentation. But, be certain that this
photo will have a prominent role in my presentation (it will likely be what is on the screen
during the Q&A at the end).
Credits
Report Created By:
Katherine Colla
Andrew Duncan
Joe Kempton
Images From:
Andrew Duncan
Starry Night Pro Software
Star Strider Software
NASA
www.astro.ucla.edu
www.lcse.umn.edu
Content based on:
Relativistic star calculator- by Stephen R. Schmitt
Solar Sail Mission Requirements document
NASA
A Relativistic Interstellar Traveller by Alexis Brandeker
www.fourmilab.ch/cship/